Automotive manufacturers have traditionally offered spare tires with the fleet of vehicles they produce. In the early days of automobiles the spare tire was mounted externally on either the running board or on a rear-mounted tire carrier. To comply with advances in styling the spare tire was concealed, most typically being moved inside the vehicle's trunk. While this arrangement provided a suitable solution for placement of the spare tire for decades, changes in fuel economy requirements dictated the need for vehicle weight reduction. Manufacturers reviewed the vehicle anew in its entirety seeking ways to reduce vehicle weight. One answer to the effort to reduce overall vehicle weight was to replace the conventional, large and bulky road tire with a smaller temporary tire or “donut.”
While the temporary tire represented a significant decrease in overall vehicle weight, the further improvement in tire design and durability as well as the concurrent general improvement in roadways gradually began to reduce the need for relying on a spare tire at all.
In response to these advances in both tire technology and road quality, vehicle auto manufacturers have begun to substitute a “temporary mobility kit” (or “TMK”) for the spare tire. The TMK includes a dual-purpose air compressor and a sealing system. The sealing system includes a sealing compound that will effectively seal most punctures caused by nails or similar objects. The air compressor drives the sealing compound into the compromised tire and, subsequently, can be used to reinflate the tire. The growing trend today is for manufacturers to equip the vehicle with a temporary mobility kit within a space provided in the vehicle, such as (but not exclusively) in the spare tire well of the trunk.
Like the spare tire which it effectively (if not actually) replaces, the temporary mobility kit is disposed well out of the way of the vehicle operator and thus is frequently overlooked as part of ordinary vehicle maintenance. However, while the sealing and flow characteristics of the sealant of the temporary mobility kit are largely resistant to the passage of time while stored in the substantially oxygen-free environment of the sealant canister, eventually attention must be given to the temporary mobility kit according to a fairly predictable schedule.
Further, when the TMK is used, it is removed from the vehicle, the tire is inflated so that repairs may be made, and the kit is typically returned to the vehicle. The TMK is designed for a single use and upon use, it must be service.
While providing clear advantages over the weight demands of the spare tire as well as providing the vehicle operator with a practical alternative over the demands of tire changing, as in most every area of vehicle technology the development of temporary mobility kits and their relation to the vehicle are in a continuing state of development.